The present invention relates to inductive flow meters.
Practitioners skilled in this art are familiar with the type of inductive flow meter having a flow channel section that is defined by an electrically insulating inside wall, with the flow channel section containing two electrodes that are diametrically opposed across a cross-section of the flow channel section and exposed to the flow medium that is under investigation. Insulated measurement signal lines are connected to the electrodes, and a magnetic field generating system that is situated outside the flow channel section is used to generate a magnetic field that passes through the flow channel section in the vicinity of the cross-section referred to above, which contains the electrodes. This magnetic field is essentially perpendicular to a connecting line between the electrodes and is perpendicular to the longitudinal axis of the flow channel section, being established between the pole shoes of the magnetic field generating system that are arranged on opposing sides of the flow channel section. The field windings of the magnetic field generating system can be energized either with direct current or with alternating current, and a measurement signal that is a function of the flow of an electrically conductive medium within the flow channel section (a DC voltage signal or an AC signal, depending on the manner in which the exciter winding of the magnetic field generating system has been energized) can be tapped off. Inductive flow meters of this general design and their method of operation are familiar to the practitioner skilled in the art.
For example, DE-OS 1 773 484 shows a measurement channel body containing the flow channel section manufactured from plastic, with the electrodes and the measurement signal lines that lead to them insert-molded. This results in a defined position of the electrodes and the measurement signal lines relative to the flow channel and reduces the costs associated with calibrating and adjusting operations for the production of large numbers of such a device.
U.S. Pat. No. 4,428,241 shows measurement signal lines that lead to the electrodes of a flow meter of the general type in question, arranged on a circuit board like a printed circuit. The circuit board is held by special retaining devices in a defined position relative to the magnetic field generating system of the flow meter, with the circuit board situated adjacent to a measurement channel body that contains the flow channel section, and a pole of the magnetic field generating system passing through an opening in the circuit board.
Publication DE-OS 3 401 377 shows and describes an inductive flow meter of the general type described above, in which the electrodes that are exposed to the flow medium are embedded in the wall of a flow channel body that contains the flow channel section. Measurement signal lines are routed from the flow channel body through peripheral and axial grooves in the pole shoe arrangement of the magnetic field generating system. However, these measurement signal lines are not held in a fixed position within narrow limits, either by the measurement channel body or by the magnetic field generating system.